A one-step carbothermal synthesis and characterization of biochar-supported nanoscale zero-valent iron (nZVI/BC) was performed for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. High dispersions of nanoscale zero-valent iron supported on biochar were successfully synthesized by the pyrolysis of an iron-impregnated biomass (corn stover) as the carbon and iron source under nitrogen atmosphere. The effects of the pyrolytic temperature on the Fe mineralogies formed on the biochar are discussed. In general, the effects of the treatment time, initial solution pH, and nZVI/BC dosage on the Cr(VI) removal are presented. The results showed high crystallinity and purity, and nZVI/BC was obtained at a pyrolytic temperature of 800 °C. The batch experimental results determined that the adsorption capacity of Cr(VI) decreases with the increase in the initial pH value from 4.0 to 10.0. The Cr(VI) adsorption kinetics data effectively followed a pseudo-second-order kinetics with a calculated rate constant of 0.0.3396 g mg⁻¹ min⁻¹. The calculated thermodynamic parameters, such as ΔG°, ΔH°, and ΔS°, were evaluated, and the results indicated that the Cr(VI) reduction on nZVI/BC was a spontaneous and endothermic process. The adsorption mechanism of Cr(VI) was investigated by XRD and XPS analyses and the results demonstrated that Cr(VI) was reduced to Cr(III) and the oxidation of nZVI occurred during the reaction process. These results prove that nZVI/BC synthesized by a one-step carbothermal method can be considered as a potential candidate for the removal of Cr(VI) from aqueous solutions.

The tartrate-intercalated MgAl layered double hydroxide (MgAl-TA LDH) was prepared by ion-exchange method at the acid solution using MgAl-CO₃ LDH as the precursor. The adsorption of Cu²⁺ on MgAl-TA LDH was studied and some influence factors such as contact time, initial Cu²⁺ concentration, adsorbent dosage, solution pH, and adsorption temperature were investigated. Three kinds of adsorption isotherms (Langmuir model, Freundlich model, and Redlich–Peterson model) were investigated; the results indicated that equilibrium was well described by Langmuir isotherm, predicting the adsorption of Cu²⁺ on MgAl-TA adsorbents was a monolayer adsorption. The equilibrium kinetic adsorption data were fitted to the pseudo-second order kinetic equation. Furthermore, the adsorption of Cu²⁺ was controlled mainly by chemical process combined with intra-particle diffusion. Parameters of adsorption thermodynamic suggested that the interaction of Cu²⁺ adsorbed by MgAl-TA LDH adsorbents was spontaneous and endothermic.